Field of the Invention
The present invention relates to a technique of scheduling wireless communication.
Description of the Related Art
A wireless LAN system represented by IEEE802.11 is widely used. In the wireless LAN, a base station called an access point (to be referred to as an “AP” hereinafter) controls a network. A wireless network is formed by the AP and stations (STAs) which fall within the radio wave coverage of the AP and are in a wirelessly connected state.
Furthermore, products and standards for various network forms of the wireless LAN have appeared on the market, in addition to this conventional simple wireless network configuration of the AP and STAs. U.S. Patent Application Publication No. 2014/0302787 describes Neighbor Awareness Networking (NAN) which is defined by Wi-Fi Alliance as a standard for discovering a communication apparatus and a service provided by it with low power consumption. This is intended to reduce the power consumption by which a communication apparatus synchronizes with another communication apparatus in terms of a duration in which information is exchanged with the other communication apparatus, and thus shortens the time during which a wireless RF (Radio Frequency) part is enabled. This synchronization duration in NAN is called a Discovery Window (DW). In NAN, communication of service information is executed in a DW duration. The DW is defined by the time and channel (such as a frequency) to be used by a plurality of devices for executing NAN communication. A set of terminals which share the schedule of DWs is called a NAN cluster.
Each communication apparatus (to be referred to as a “NAN device” hereinafter) belonging to the NAN cluster operates in one of master, non-master sync, and non-master non-sync roles. The NAN device operating in the master role periodically transmits a synchronization beacon (to be referred to as a “sync beacon” hereinafter) as a beacon for causing another terminal to identify the DW and synchronize with the DW duration. In addition, the NAN device operating in the master role transmits a discovery beacon as a signal for causing a terminal, which does not belong to the NAN cluster, to recognize the NAN cluster. The discovery beacon is transmitted in a duration other than the DW durations, for example, every 100 ms. Note that at least one NAN device in each NAN cluster operates in the master role. The NAN device operating in the non-master sync role transmits not a discovery beacon but a sync beacon. The NAN device operating in the non-master non-sync role transmits neither a sync beacon nor a discovery beacon.
The NAN device joining the NAN cluster executes communication about service information in the DW duration by synchronizing with the DW duration which comes every predetermined cycle in accordance with the sync beacon transmitted in the NAN cluster. More specifically, the NAN device transmits or receives at least one of a subscribe message as a signal for discovering a service and a publish message as a signal for sending a notification of provision of a service. Furthermore, the NAN device can transmit/receive follow-up messages for exchanging additional information about a service in the DW duration. Note that the publish, subscribe, and follow-up messages will be collectively referred to as service discovery frames (SDFs) hereinafter. The respective NAN devices can advertise or detect the service by transmitting/receiving the SDFs. The SDF includes a service ID as an identifier for identifying a target service. The NAN device can discover/detect a service by transmitting/receiving SDFs to/from another NAN device.
When the NAN device performs communication of an application for actually executing a service after discovering/detecting the service, it can establish not NAN but post NAN. Post NAN is a network different from NAN, such as an infrastructure network, IBSS, or Wi-Fi Direct. The NAN device establishes post NAN, thereby allowing communication by the application. Note that the NAN device can also perform communication by establishing a NAN data link not in post NAN but in the NAN system. That is, the NAN device can communicate with another NAN device in the NAN cluster by setting a communication duration other than the DW durations in NAN without setting a network different from NAN.
The communication duration of the application between the NAN device and another apparatus in the NAN cluster can overlap the DW duration of another nearby NAN cluster to which the NAN device does not belong. In this case, a wireless signal by the application may have an influence on, for example interfere with, a wireless signal to be transmitted/received in the DW duration of the nearby NAN cluster. That is, the wireless signal by the application may inhibit communication in the DW duration of another NAN cluster.
Similarly, even in a system other than the NAN system, the same problem may arise if the system sets a duration of a predetermined time length which periodically comes, and performs communication in the duration, and can further perform communication in a duration other than that duration.
According to the present invention, a communication apparatus performs communication without inhibiting communication of another apparatus in a duration which periodically comes.